Electric alarm circuit



Aug. 13, 1935.

R. W. MCBRIEN El AL ELECTRIC ALARM CIRCUIT Filed July 24, 1931 /4 Y 7g@ I n /g/ /44 Z'crc L /5 I 2\ /5 u /3 l mera/05W@ 3/ 3 3', ,59 5MM I I I I I I I I I I I I I l i //o va Lrs POWER ClCUlT VPatented Aug. 13, 1935 P -d N 42,011,112

` e e 2,011,112 A ELECTRIC ALARM CIRCUIT Roger William Mcrien, Alton, and Norval Floyd Wilson, East Alton, Ill.; said Wilson assignor to l said McBrien UNI-TED STATES PATENT OFFICE Application .luly'24, 1931, Serial No. 552,904

' A zolaims. (01111-356) Our invention has relation to improvements in electric alarm I'circuits and it` consistsvin the `novel features ci constructionl more fullyv set forth in the specification and pointed out in. the claims. 'I'he invention is particularly directed to an alarm circuit that may be connected to the various power 'circuits in buildings pand residences primarily forsounding, or otherwise giving-an alarm in case of iire, and secondarily for permanently `opening a circuit that has been shorted. 'I I I The objects of the invention are to provide a comparatively simple alarm circuit that is certain in its operation; one that embodies means for 1 disconnecting fromI the line any circuit of a series that has been shorted so that the operation of the alarm in other circuits may not be impaired; one in which a single switch is capable of responding either to heat or a short in any of the power circuits; .one in which theA action is produced by a relay in each power circuit,said relay being associatedwith a fuse, the replacementof which automatically sets the relay. Furjther and other advantages will be better. ap- 2" parent from a detailed description of the invention in connection with the accompanying drawingin which: e e Figure lis a `diagrammatic View of our improved alarm circuit applied to two power circuits connected in parallel; Fig. 2Iis a cross-sec- Ational detail through apart of the panelon which the associated relays and fuse plugs are mounted; Fig. 3 is a side elevation withfparts broken away of our speciallyI designed oscillating ,35 switch for selectively closing the proper Acircuit depending on whether the switch has been actuated by` a re or by a short circuit. Referring to the drawing, the` power or work circuitscomprise conductors I, 2, and `2', conlductor I being directly connected to 'line wire L and Yconductor 2*.being connected to line wire L' by a conductor 3 and a conductor 4 between which fuses 5 and 6 are connected'in series. Conductor 2 is similarly connected toline wire L i by conductors 3' and 4', between which are fuses 5 and 6. Fuses 5 and 5' areIcapable ofI carrying a heavier load (approximately 20 amp.) than 1 'the fuses 6 and 6 (l0-amp.) .I: The adjacent ends of fuses I5 and 6 are connected to a single pole `switch 'IV by a conductor "8,1and adjacent' ends of fuses 5" and 6 are connectedto a single pole switch'l" by a conductor 8. Switches 1 and 1 are normally held out of contact with contacts Sjand 9 by triggers Illand I0 whichcomprise armatures within coils Iland II'. Corresponding ends of'coils II and I I' are connected to line wire L'V by conductors I2 and I2' respectively, while the opposite corresponding endsof coils II, II are connected to armatures I0, I0' respec- 5 tively. The switches 1, Il and associated parts just described constitute relays for connecting ,their respective power circuits 'to the alarm 'circuit should a fire or a short circuit occur in one of the power circuits,` as will be more apparent 10 hereinafter. Our alarm circuit is primarily intended to give an alarmlin case of` a fire, consequently, tliermostatic'switches of any common type are distributed throughout `the 'building that is protected by` our invention. Each thermostatic 15 switch I3 is connected in series with a flasher,

or blinker,` comprising contacts I4 and I5, and

a coil of nichrome` wire I6 which is designed'cn being heated by a flow of current; to separate theV contacts, thus interrupting the flow of current. 2O As the coilcools, the contacts again come to,- gether, producing a I continuously" interrupted flow of current acrossthe conductorsof the circuit. I I i I I The foregoing descriptionsh'ows that fuses 6 25 and 6 and coils IIIand II' are in parallel-series connection with the powercircuit and that when these circuits are operating underload, current will fiow through the fuses 6 and 6. However, when either of the thermostatic switches I3 are 30 closed there Vwill be a heavy current iiow through either fusel 6 or '6' because the asher coil I6 is of low resistance and the fuses 6 and 6', depending on which switch I3 is closed, will be blown and cause the current to flow through 35 eithercoil Il or II. Assuming that the thermo'- static switch I3 in the power circuit comprising conductors I and 2 closes, the coil I I `will be energized and will withdraw the trigger I0 from the switch 1, allowing said switch to be closed 40 on the contact 9 under the influence of a spring Il (see Fig. 2). Y I s At this point it should be pointed out that a transformer T. has its primary winding connected acrossthe line by meansof conductors I8 and I9 45 leading to one endof` said windingV and conductor 1 20 leading fromthe other end of the winding to a trigger armature 2| normally operating to hold the switch 22 out of engagement with a contact 23, the pivot end of switch-22 being connected 50 to line wire L bya conductor 24. Thus, the transformer primary winding is connected directly across the 1-10 volt line. The secondary winding `of the transformer T is connected to the primary winding by a conductoiyfii andlat the` opposite ,55

end to a coil 21 by a conductor 25, the opposite end of said coil being connected to the switch contact 28 by a conductor 29. A switch lever 30 has its free end normally engaged with contact 28 and its pivot end connected by a conductor 3| to each of the contacts 9 and 9. It is thus apparent that the circuit of the transformer secondary .is closed when either of the switch levers 1, 1 engage contact '9 or 9. We have assumed that the switch 1 has been closed on vthe contact 9 and we will trace the transformer1 secondary circuit through this connection: from one end of the transformer secondary throughkconduc'tor 28 to the coil 21, thence through conductor 29 .to

contact 28, switch lever 3B through conductor 3i to contact 9; the path of the current'is then through switch lever 1, conductor 8, fuse 5, conductor 3, to conductor 2, throughtheclosedswitch I3 and flasher (elements I4, l5, and t5) -toconductor l and line wire L to conductor "2B, switch -lever=22, armature 2i, conductorlll and transkformer secondary. The actuation'of 'the switch 7lever 1breaks the connection between the vpower Ivor work circuit and the line `:and `connects the jtransformer secondary in -serieszwith the power circuit. This results in the` flow of a low voltage current from the transformer secondary through `the coil .21Jand the flasher (elements It, l5, `and 1.6) causing current tointermittentlypass through the 'coil 21 and intermittentlyattract armature 32 depending fromlfioat A33 within casing 34.

`The casing 3@ and its associated parts about `to be Vdescribed comprise an oscillating switch 'for selectively closing thegalarrn circuit, or the :safetyfcircuit about to be described. The casing v3Lhas awell it-dependingr from it normally lled with mercury to the level indicated by :J: in the 'diagram and a partition 33 divides the casing into two compartments 31 and 38; Thereis a small .port 36 at the-bottom-of the Apartition 33. YCompartment 31 houses the oat 33 with its dependingjarmature 32 extendinginto thewell 35 and -compartment 38 has contacts 39 and 40 extending into it, the latter being somewhat longer, and of course, closer to the level ofi the mercury when lthe thermostatic switch is inactive. r There `is also a contact V13| Vextending linto the-bottom-of the wellV 35 andmaking permanent velectric connec- .tion with the mercury.r The intermittent iiow of low voltage-current through the coil 2:1 causes the vfloat 33 to bob up and down, or -oscillate in the mercury, displacing some of the mercury which splashes over the partition 36 into compartment 38, raising the vlevel thereinV until the mercury touches contact EL v When thisrcontact is made between the vmercuryand the contact '40, the oscillating switch circuit which closes the alarm circuit is activated. This oscillating switch circuit is as follows: from conductor I8 to contact il [through the mercury incasing 34 to contact d, through conductor '42 to the thermo-electric element 33, through conductor 44 lto coil 45 associated with-armature 2*1, through said armature and switch 22 to conductor 24 and line wire L. The thermo-electric switch comprises a'high resistance coil 4S anda pair of contacts 631, 41 vin parallel therewith and adapted to Abe closed bythe warpingaction produced when thercoil i6 becomes suiiiciently heated. The coil llis of 'sufficiently high resistance -so' there willnot kbe renough current flowing through coil 135 to 'attract armature ,2l until the contacts 41, t1 have been 'brought' together. The reason forthisis to guard against an accidental closing of switch Y22 with contact 23. It will take'approximately 40 seconds forthe coil 46 to become sumciently v'heated to close V"the the transformer primary circuit. Thus, it is apparentithat vif any of the thermostatic switches I3 are closed and remain closed for an appreci- Aable length of time, the alarm relay is actuated to close Ithealarm circuit, producing the alarm at the lire department, or in other suitable places. 'Some provision .must be made for preventing the alarm circuit from being actuated, or put out of commission, by a short in any of the power icircults. We :therefor'enembody in Ithe invention V-afsafetycircuitrshould a permanent-short develop in any .of the power. circuits as'follows. We will assume:thati`conductors1 .anduZ comprising onefof the power circuits are shorted so as to cutout the -resistance Aof the load on .this circuit. This will 'cause acurrentow as before through fuses 5 `and 73 resulting in 'the blowing. of zthe lower lcapacity fuse tgwhereupon thecurrent will then `flow through coil ll l and actuatearmature. Il) con- `necting switch lever 1 with contact i9 as before. This will produce a steady iiow of current through `coill-f1 instead of an intermittent Acurrentand .the

oat 33 will beldrawn downwardly into the inercury in casinff3tand held down so as to cause the Y displaced mercury to contact with vthe terminal 39 which is connected to a highresistance coil t9 similar to-coilft 'The coillg isalso connected lto conductor' 3l by-aconductor 5950 that there will be a flow of `current at line voltage through the -coilfmv lAs'this coil becomes heated, contacts 5l,

52willbe warped together thus'providing a shunt 'path Vfor the current through-contactsil ,-52, conductor '53 and-coil-54 which fisadapted to-actuate an armature 55 cooperatively connected with switch lever 38. It may be mentioned at this time thatfthegap between contacts Eiland-521m shorter than the gap between contacts 61,141 so that, although current is owing 'through resistance 46 at the -same 'time current is iiowing through resistance `49, the alarmcircuit will not be closed "because the safety switch actuating circuit, in-

`cluding contactsl and 52 will rst close-and' pro- `videa comparatively low resistance circuit for the'current. The energizing of coil 514 attracts the armature andmoves the switch lever Vaway 'from contact 23 and into engagement-with con tact'L Sincecontact 511s connected by'a con- 'd'uctor 58 and conductor i8 to line wire L', and Vvswitch lever 3Q is connected by conductor 3i, switch lever E and the shorted power circuit to `.line wire L, there will be an excessive current flow 'through this lpower `circuit'resulting in the blow- 'irigof'the heavier fuse 5, vthus opening this particular power circuit. Of course, Vwhen this cir- 'cuitY isopened, safety Vswitch lever YEllis restored Yto its normal position in contact with the contact '28 and-the entire alarm circuitagain becomes linactiveand `in condition Ifor service in the event lthermost'atie switchz=l31inany other of the power Vcircuits is .'closed.r Thus, -a-short circuit does not interfere vwith the operation of my improved 'alarm circuit, but merely-results inthe particular power circuit having the short being temporarily `'disconnected from service. K ,Y

.. The fuse plugs 6 and 6'.. are mountedjin a con- Vcause the alarm VB. to 'be sounded. The action -ventional manner on a panel `59, as are also fuse `plugs 5, 5'; Switch levers1, 1 aremounted on panel 69 secured in spaced relation to the panel 59. The upper part of the switchleversd, 1' are each forked so as to receive a pin p which'is `adapted to make contact between fuseB or 6 and the holding clip 6 Ifor fuse 5 or5. A contact62 connects clip 6I with a connecting post 63 extending betweenrpanels 59 and 6I), and a yieldingcontact 64 connects the post 63with` pinp. The pin p has a coiled spring 65 mounted on i-t between the panel 59 and a sleeve 66, said spring being held under tension when the fuse plug 6 is in place.

` When the switch lever 1 is set as shown in the diagram (Fig. 1 and Fig. 2), it is spaced from the shoulder 66' so that on retracting the trigger armature I6, it may be forced into contact with the contact 9 under the tension of the spring I1. As we have seen, when this contact is made be tween switch lever 1 and contact 9 the fuse 6 has been blown and it must be replaced in order to restore the circuit to operative condition. In removing the plug 6 the spring 65 forces the pin p "into the socket of fuse plug 6, shoulder 6B rocking the lever 1 behind the armature trigger I0, thus resetting the relay. When the new fuse plug 6 is put into the plug socket the pin p will be forced `through the panel 60 to a greater extent and shoulder 66 will be withdrawn from contact with the switch lever 1, allowing said lever freedom to again snap into engagement with contact 9.

We will assume that switch levers 1 and 1 are set as shown in the diagram of Fig. 1 and in Fig. 2, and that the switch lever 22 is also set as shown in -the diagram. The circuits are now in condition for operation and if either thermostatic switch I3 is closed by the heat caused by a fire in the building, current will of course flow through that particular power circuit intermittently because of the action of the flasher contacts I4 and I5. The resistance of the flasher coil I6 is low so that on the first current impulse the fuse 6 or 6 will be blown, thus insuring an intermittent flowof current through switch 1, armature IIJ and coil II, which is energized to release the` switch 1, whereupon it is forced by the spring I1 (Fig; 2) into engagement with. contact 9. This movement of the switch 1 brings into action the oscillating `switch comprising the casing 34 and associated parts. The actuating current for the oscillating switch comes from the secondary of transformer `T, the circuit including coil 21, switch lever Si),

contact 9, switch lever 1, flasher contacts I4 and i5, line wire L, switch 22, armature 2l, conductors 29 and 25, as above pointed out. We thus have a small current flow from the secondary of transformer T impressed on the coil 21 which produces an oscillating movement of the iioat 33 due to the fact that flashers (I4, I5, and I 6) are in the circuit. This constantly oscillating float agi- Y 41 resistance in the circuit is reduced and the armature 2| actuated to release switch 22 which (under the influence of a spring not shown) engages contact 23 to close the alarm circuit and just described takesplace` in case of a re in the building and the `consequent closing of thermostatic switches I3. y i

`Should the power circuit, comprising conductors I andv 2, or Iv and 2', be shorted `it is obvious that thezflasher will not come into operation but the flowthrough the circuit will be steady so that lthe float 33 instead of oscillating will be held down by continuouslenergy inthe coil 21.` `The down,-

wardmovement of, thefloatr33displaces enough Y ysaid'coil to actuate the armature 55 into engagement with contact 51. Since contact 51, as above pointed out, is connected to line wire L',and since the switch 30 is connected in the shorted power circuit, there will immediately be a heavy flow of current through 20 ampere fuse 5 causing this fuse to be blown to put the circuit out of commission before the alarm circuit has been actuated. The reason the alarm circuit isnot actu-A ated is because contacts 5Iand 52 come'together before contacts 41, 41 can come into engagement.

The foregoing shows clearly that we have `a. positively acting alarm4 circuit to indicate the presence of a re in a building equipped with our device, safety means being embodied to not only prevent the sounding of an alarm but also to put the particular circuit affected out of commission in case of a short developing in said circuit.

Having described our invention, we claim:

1. A composite work circuit and alarm circuit comprisinga work circuit including a fuse in series therewith, a relay having its winding in shunt to the fuse, a normally open alarm switch, a flasher switch having flasher contacts and flasher contacts control means, a connection to the work circuit including in series the alarm switch, the asher contacts, the flasher control means and` the fuse, whereby when the alarm switch closes or upon the occurrence of a short in the work circuit the fuse will blow and remove the shunt across the relay winding, an oscillating switching means comprising means for closingone circuit only upon oscillation thereof or this one circuit and another circuit upon permanent operation thereof, electromagnetic means for operating the switching means, means operated by the relay when its winding is energized for connecting the work circuit with the switching means operating means, whereby in case of the closure of the alarm switch the switching means will be oscillated while in case of a short in the work circuit the switching means will be permanently operated, an alarm and means controlled by said circuits to differentiate between the closure of said one circuit or the closure of both circuits and operate the alarm only on the closure of -said one circuit. y

2. A composite work circuit and alarm circuit comprising a work circuit including a fuse in series therewith, a relay having its winding in shunt to the fuse, a normally open alarm switch, a low voltage switch having flasher contacts and flasher contacts control means, ai connection to the work circuit including in series the alarm switch, the flasher contacts, the flasher control means and the fuse, whereby when the `alarm switch closes or upon the occurrence of a short inltne work crcuitsthe .fuse wllblowand'remove thefs'hunt across'the relay Winding, .an oscillating Lswitching means :comprising means 'for closing one circuit only upon oscillation thereof or this Vone circuit and another circuit vupon ypermanent operation lthereof, electromagnetic `meanslfor operating the-switching means, meansoperated .by the relay when its Windingis energizedtodisconlnect the Working circuit fr'om `its Ihigh voltage vpower source and connect the work circuit Withra :low .Voltage .power sourceand the switchingmeans -op'eratingmeans,Wherebyin case yof theclosure of the alarzmfswitch the switching means Will'be oscillated While'in case of a short in the Work circuit 'the-switchingmeans Willbe permanently operatied, 'an alarm and means controlled by said circuits ROGER WILLIAM MCBRIEN. :NORVAL FLOYD WILSON. 

